MeSH is an acronym for Medical Subject Headings. It is the National Library of Medicine's (NLM) controlled vocabulary for indexing the articles found in PubMed.
MeSH terms are very helpful when searching for articles in PubMed. From the PubMed homepage, use the drop-down menu at the top left to search the MeSH database. Once you locate your term on the MeSH hierarchy, check the box next to it and then use the drop down menu above the results to "Send To the Search Box with AND." You can then do a second search for another MeSH term and combine these terms in the search box.